Lipari: Volcanological History

The seven Aeolian islands (Alicudi, Filicudi, Salina, Lipari, Vulcano, Panarea, and Stromboli) represent the emerged portion of volcanic apparatuses forming the semicircular aeolian volcanic arc (Fig.1); this geologic structure, about 200 km long, also comprises the submarine volcanoes (seamounts) of Eolo, Enarete, Sisifo (western sector), and Lametini, Alcione (eastern sector).eolie
Lipari, the largest island of the Aeolian archipelago (37.6 Km2),  is the emerged portion of a huge volcanic apparatus about 1,500 meters high: starting from the sea floor, at a depth of about 1,000 metres below sea level,  it arrives to the 602 metres above sea level of Monte Chirica.
The oldest outcropping rocks in the island have an age of 223,000 years Before Present (BP), the youngest ones (Monte Pilato, Forgia Vecchia) date back to the 6th century AD: this last, recent age emphasises that, from a volcanological point of view, the Lipari "volcano" must be considered still active. Actually, the only evidences of volcanic activity are represented by fumaroles and hot springs: low-temperature fumaroles (80-90°C) are present  both in the western (between Timpone Pataso and Timpone Ospedale) and in the southern (Vallone Ponte) sectors of the island, whereas hot springs (57°C) are located in correspondence with Terme di San Calogero and Bagno Secco. Fumarolic activity in the western sector of Lipari is responsible for the intense alteration of the volcanic rocks in the area, consisting in a widespread chaolinization (chaolin was already exploited by Greeks).
The fairly complicate, geologic framework of Lipari is the combination of several volcanic episodes related to two stages of magmatic activity separated by a stage characterised by important erosional episodes.
The first stage (pre-erosional) consists of two periods (first and second) of volcanic activity characterised by the emplacement of calcalkaline (CA) to high-K calcalkaline (HKCA) products whose composition ranges from  basaltic-andesite to andesite.
The second stage (erosional) is characterised by one period (third) during which both volcanic activity (HK-CA andesitic products) and marine erosional activity (formation of abrasion paleo-surfaces and relative pebble-sand deposits: marine conglomerates) coexisted.
The third stage (post-erosional) consists of two periods (fourth and fifth) of volcanic activity whose products exhibit more potassic character (from HKCA to shoshonite = SHO) and more evolved compositions (rhyolite).

figura 2The volcanic activity of the first period (Paleolipari: from about 223,000 to 150,000 years BP) is related to the activity of several monogenic centres (scoria- and lava-cones) located along the western coast (Fig.2) in correspondence with a NW-SE-oriented tectonic lineament. They are characterised by prevailing strombolian (scoriaceous deposits) or effusive activity (lava flows) and very subordinate hydromagmatic activity (tuff and lapilli tuff): their products display CA basaltic-andesite compositions. Almost contemporaneously, and with similar volcanological and compositional features, the twin volcanic centres of Monterosa and the monogenic centre of Timpone Croci, begin their activity in the central-eastern sector of Lipari.
All these centres, actually strongly eroded, covered by younger volcanic products, crossed by dykes and locally highly fumarolized, represent the remnants of the Paleolipari apparatus.

The volcanic activity of the second period (Monte Chirica I and Monte S.Angelo I centres: from less than 150,000 to 127,000 years BP) begins in the central sector of Lipari with the emplacement of volcanic products related to the large Monte Chirica stratovolcano (Fig.3). To the early explosive activity of Monte Chirica (Monte Chirica I) must be ascribed the thick and well stratified sequence of massive tuffs and scoriaceous lapilli tuffs cropping out along the steep canyons going down from the top of Monte Chirica to the Acquacalda seashore; the few remnants of the HKCA basaltic-andesite lava flows (at places, strongly fumarolized) are visible only around the crater area (Chirica Rasa), near the top.
The early volcanic activity of the huge Monte S.Angelo stratovolcano (Monte S.Angelo I) represents the first extensive example of magma-water interaction testified by the emplacement of hydromagmatic, well stratified, HKCA andesitic pyroclastics cropping out near Timpone Ricotta and in the Timpone del Corvo ­ Marina di Porto Salvo area (the tourist harbour of Lipari). The sequence of lapilli tuffs and ash tuffs represents the hydromagmatic phase (i.e. a prevailing explosive phase), followed by an effusive phase characterised by the emplacement of thick HKCA andesitic lava flows.figura 3

After a period of quiescence, indicated both by a well evident subaerial erosional surface and by marine erosional surfaces with related marine conglomerates, the volcanic activity starts again: the third period comprises a time span ranging from 104,000 until to about 90,000 years BP This  period (Monte S.Angelo II and III, Monte Chirica II) is characterised by the emission of volcanic products with fairly similar composition (HKCA andesite) but with very different eruptive style as testified by the hydromagmatic - effusive contemporaneous activity of the two large poligenic centres growing up in the central sector of the island: Monte Sant'Angelo and Monte Chirica (Fig.4).
The Monte Sant'Angelo poligenic centre, already active during the previous second period, begins its new activity (Monte S.Angelo II) with the emplacement of thinly bedded layers of grey, andesitic lapilli tuffs frequently reworked and enriched in remains of plants and leaves: mainly trunks, stumps and leaves of palms and olive-trees. Near Timpone Pataso, these deposits are strongly reworked being the result of the filling of a small lacustrine basin and show intercalations of silica-rich (chert) levels. This explosive activity is followed by the emplacement of "cordierite-bearing andesite" lava flows, a magma-type suggesting the partial assimilation of "crustal" material.
figura4The last moment of activity of the Monte S.Angelo poligenic centre (Monte S.Angelo III) is testified by thick, massive, poorly bedded pyroclastics forming the top of the stratovolcano and by small andesitic lava flows.
As for the northernmost poligenic centre of Monte Chirica, the renewal of volcanic activity (Monte Chirica II) takes place with the emplacement of thick HKCA andesitic lava flows, arriving to the sea near Cala Sciabeca.
During the building of these volcanic centres, some other episodes of marine erosional activity take place: the result of these repeated processes consists in the formation of some ancient shorelines, and of their relative marine conglomerates (beach-deposits with highly rounded pebbles), that are visible mainly along the western cliff of Lipari at the variable height of 2-45 m above sea level.

At this point, a significative period of volcanic quiescence (about 50,000 years long) separates the end of the erosional stage from the beginning of the post-erosional one. The renewal of volcanic activity starts at 42,000 years BP and corresponds to a marked change in eruptive style and magma composition: all the third stage is characterised by the emission of much more evolved magmatic products (rhyolite) giving rise to squat lavic bodies (domes and obsidian lava-flows) and to large amounts of pyroclastics (pumice deposits).
The volcanic centres active during the fourth period (Fig.5) are located in the southern sector of the island: their white pyroclastic products are recognisable owing to the presence of peculiar intercalations of brownish pyroclastic deposits of exotic provenance (Brown Tuff). The volcanic activity (from 42,000 to 20,300 years BP) is related to the three centres of Punta del Perciato, Falcone and Monte Guardia characterised by similar schemes of evolution: early hydromagmatic explosive episodes (surge and fall deposits) are followed by the outpouring of highly viscous rhyolitic domes. The domes of Punta del Perciato centre, almost uniquely visible under the present sea level, crop out discontinuously along the south-western coast, at the base of the cliff; the domes of Falcone centre, Capparo and Capistello, crop out over the previous domic products in the southernmost portion of Lipari, whereas the domes related to the Monte Guardia centre  are located in the high south-western sector (S.Lazzaro, Monte Guardia, Monte Giardina) and in the south-eastern one of Lipari (Castello, S.Nicola, Punta S.Giuseppe).

figura 6The volcanic activity of the fifth period (between 16,800 and 1,400 years BP), is confined to the north-eastern sector (Fig.6), and is related to the activity of four centres: Canneto Dentro, Gabellotto, Monte Pilato and Forgia Vecchia.
The activity of Canneto Dentro is testified only by limited outcroppings of pumiceous pyroclastic breccia and of a squat rhyolitic dome. The activity of Gabellotto begins with the emplacement of large amounts of white, pumiceous pyroclastics (dry surge deposits) leading to the building of a tuff ring, and ends (between 11,400 and 8,600 years BP) with the outpouring of a huge, obsidianaceous, rhyolitic lava dome. After a volcanic inactivity about 3,000 years long, marked by the formation of an orange-red paleosol, the activity of Monte Pilato, located in the northernmost sector of Lipari, starts with a series of explosive eruptions leading to the building of a large rhyolitic pumice cone from which the obsidianaceous and rhyolitic lava flow of Rocche Rosse, about 20 meters thick,  overflows reaching the sea nearby Acquacalda.  The last volcanic products are related to the activity of Forgia Vecchia (about 1,400 years BP) and consist in the emplacement of few white, pumiceous pyroclastic deposits followed by the outpouring of a viscous, bilobate, rhyolitic lava flow: this is the last demonstration of volcanic activity on Lipari.

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